Polymorph-Dependent Phosphorescence of Cyclometalated Platinum(II) Complexes and Its Relation to Non-covalent Interactions

Elina V Sokolova; Mikhail A Kinzhalov; Andrey S Smirnov; Anna M Cheranyova; Daniil M Ivanov; Vadim Yu Kukushkin; Nadezhda A Bokach

doi:10.1021/acsomega.2c04110

Polymorph-Dependent Phosphorescence of Cyclometalated Platinum(II) Complexes and Its Relation to Non-covalent Interactions

ACS Omega. 2022 Sep 13;7(38):34454-34462. doi: 10.1021/acsomega.2c04110. eCollection 2022 Sep 27.

Authors

Elina V Sokolova¹, Mikhail A Kinzhalov^{1

2}, Andrey S Smirnov¹, Anna M Cheranyova¹, Daniil M Ivanov^{1

2}, Vadim Yu Kukushkin^{1

3}, Nadezhda A Bokach^{1

2}

Affiliations

¹ Saint Petersburg State University, Universitetskaya Nab. 7/9, Saint Petersburg 199034, Russian Federation.
² Research School of Chemistry and Applied Biomedical Sciences, Tomsk Polytechnic University, Tomsk 634050, Russian Federation.
³ Institute of Chemistry and Pharmaceutical Technologies, Altai State University, Barnaul 656049, Russian Federation.

Abstract

Cyclometalated platinum(II) complexes [Pt(ppy)Cl(CNAr)] (ppy = 2-phenylpyridinato-C²,N; Ar = C₆H₄-2-I 1, C₆H₄-4-I 2, C₆H₃-2-F-4-I 3, and C₆H₃-2,4-I₂ 4) bearing ancillary isocyanide ligands were obtained by the bridge-splitting reaction between the dimer [Pt(ppy)(μ-Cl)]₂ and 2 equiv any one of the corresponding CNAr. Complex 2 was crystallized in two polymorphic forms, namely, 2 ^I and 2 ^II, exhibiting green (emission quantum yield of 0.5%) and orange (emission quantum yield of 12%) phosphorescence, respectively. Structure-directing non-covalent contacts in these polymorphs were verified by a combination of experimental (X-ray diffraction) and theoretical methods (NCIplot analysis, combined electron localization function (ELF), and Bader quantum theory of atoms in molecules (QTAIM analysis)). A noticeable difference in the spectrum of non-covalent interactions of 2 ^I and 2 ^II is seen in the Pt···Pt interactions in 2 ^II and absence of these metallophilic contacts in 2 ^I. The other solid luminophores, namely, 1, 3 ^I-II, 4, and 4·CHCl₃, exhibit green luminescence; their structures include intermolecular C-I···Cl-Pt halogen bonds as the structure-directing interactions. Crystals of 1, 2 ^I, 3 ^I, 3 ^II, 4, and 4·CHCl₃ demonstrated a reversible mechanochromic color change achieved by mechanical grinding (green to orange) and solvent adsorption (orange to green).